Synchronize Person Assignments from Position is not working

Hello experts,

we have this issue wherein one of our employees has taken on a Secondment position. However, all his direct reports from the suspended assignment follows him in his new secondment position. Please note that we are following Position Hierarchy.

Please advise why they are not his directs on the suspended profile (or reporting to the grandparent position of the suspended assignment). It seems that his direct reports are following the manager.

Thanks